Function in C

Concept of Function in C

Imagine trying to develop a huge program like the Windows or Mac OS with hundreds of thousands (or millions of lines of code). No way to do it all in one big program file. Is the work of hundreds of computer programmers, each working on smaller pieces of the problem that are then brought together.

What is a Function?

A function is a block of code that has a name and it has a property that it is reusable i.e. it can be executed from as many different points in a C Program as required.

A complex problem is often easier to solve by dividing it into several smaller parts, each of which can be solved by itself.

main()  function  uses these functions to solve the original problem.

There are two type of function

1)Built in function

2)User Defined function

Built in Function:

C has many built-in functions that you can use in your programs.

main()

printf(), scanf(), pow() etc…..

User Defined function

If you have a special set of instructions that aren’t in a built-in function, you can create a user-defined function. Here are the steps:

A function definition has the following syntax:

            <type> <function name>(<parameter list>){

                        <local declarations>

                        <sequence of statements>

            }

For example: Definition of a function that computes the absolute value of an integer:

int absolute(int x){

     if (x >= 0)   return x;

     else                        return -x;

}

Why Should we use function in C?

1)Break a large problem into smaller pieces.Smaller pieces sometimes called ‘modules’ or ‘subroutines’ or ‘procedures’ or functions

2) Helps manage complexity, Smaller blocks of code and Easier to read

3) Encourages re-use of code

4) Allows independent development of code

5) Provides a layer of ‘abstraction’  for example a=sqrt(9.0);

Functions  Structure

Functions -Mathematical View

Functions - Example